Sadly, unless you changed the setting in the Palm itself from USB or Cradle to serial or back to USB/Cradle, the PDA could have suffered a electronics failure on its USB port. The Palm m50x had a similar bad run of luck since the designer didn't take care to handle ESD (Electro-Static Discharge.)
To determine if the PDA is broken, you need another PDA to put in the cradle. If you can't set the Hotsync in the PDA to it's cradle setting and same on the PC, then you may need someone to show you these settings. I couldn't tell if you were in-the-know about this.
I have a Sony Clie T615c that just recently started having problems with Hotsync. I get an error message on the PDA which states that "the connection between your handheld and desktop could not be established. Please check your setup and try again." I have been unable to Hotsync as a result.
My USB ports work fine with other peripherals, and I also tried using another cradle and USB cable for the PDA and received the same error message. I also tried reinstalling the Palm desktop and Hotsync software.
I didn't change any settings prior to getting the error and have no idea what the problem is. Could someone please help me?